The present invention relates generally to operations performed within subterranean wells and, in an embodiment described herein, more particularly provides apparatus and methods for controlling fluid flow within a subterranean well.
In horizontal well open hole completions, fluid migration has typically been controlled by positioning a production tubing string within the horizontal wellbore intersecting a formation. An annulus formed between the wellbore and the tubing string is then packed with gravel. A longitudinally spaced apart series of sliding sleeve valves in the tubing string provides fluid communication with selected portions of the formation in relatively close proximity to an open valve, while somewhat restricting fluid communication with portions of the formation at greater distances from an open valve. In this manner, water and gas coning may be reduced in some portions of the formation by closing selected ones of the valves, while not affecting production from other portions of the formation.
Unfortunately, the above method has proved unsatisfactory, inconvenient and inefficient for a variety of reasons. First, the gravel pack in the annulus does not provide sufficient fluid restriction to significantly prevent fluid migration longitudinally through the wellbore. Thus, an open valve in the tubing string may produce a significant volume of fluid from a portion of the formation longitudinally remote from the valve. However, providing additional fluid restriction in the gravel pack in order to prevent fluid migration longitudinally therethrough would also deleteriously affect production of fluid from a portion of the formation opposite an open valve.
Second, it is difficult to achieve a uniform gravel pack in horizontal well completions. In many cases the gravel pack will be less dense and/or contain voids in the upper portion of the annulus. This situation results in a substantially unrestricted longitudinal flow path for migration of fluids in the wellbore.
Third, in those methods which utilize the spaced apart series of sliding sleeve valves, intervention into the well is typically required to open or close selected ones of the valves. Such intervention usually requires commissioning a slickline rig, wireline rig, coiled tubing rig, or other equipment, and is very time-consuming and expensive to perform. Furthermore, well conditions may prevent or hinder these operations.
Therefore, it would be advantageous to provide a method of controlling fluid flow within a subterranean well, which method does not rely on a gravel pack for restricting fluid flow longitudinally through the wellbore. Additionally, it would be advantageous to provide associated apparatus which permits an operator to produce or inject fluid from or into a selected portion of a formation intersected by the well. These methods and apparatus would be useful in open hole, as well as cased hole, completions.
It would also be advantageous to provide a method of controlling fluid flow within a well, which does not require intervention into the well for its performance. Such method would permit remote control of the operation, without the need to kill the well or pass equipment through the wellbore.